Improvement in duplex telegraphs



r.- A. EDISON. DUPLEX TELEGRAPH.

No.178,ZZ3. Pate n-ted May 30; 1876.

MAIN LINE MAIN BATTERY GROUND UNITED STATES THOMAS A. EDISON, or NEWARKJNEW JERSEY, AssieNoR 0F ONE-HALE PATENT OFFIGEi His RIGHT TO GEORGE B. r'nnsoornor NEW YORK .oITY.

IMPROVEMENT IN DUPLEX TELEGRAPHS.

Specification forming part of Letters Patent No- 17S,223, dated May 30, 1876; application filed 4 September 1, 1874.

To all whom it may concern.-

Be-it known that I, THOMAS A. EDISON, of Newark, Essex county, New Jersey, have invented an Improvement in Duplex Telegraphs, of which the following is a specificaion:

The transmitting-battery is connected with the line by a lever that simultaneously breaks the earth-connection, so as not to interrupt the continuity of the circuit. The current sent divides and operates equally in two helices. In one helix there is a sliding core that moves with the armature of the other helix, and this latter responds to the pulsation from the distant instrument and closes a local circuit to a sounder or other receiving instrument, and there is a mechanical device that serves to compensate the attrac tion-in one of -the magnets that is due to.

the reverse action of the static discharge, thereby causing the forces to be accurately balanced.

In the diagram of the drawin the transmitting-key a opens and closes the local circuit of battery b to the helices of the electromagnets c and d. g

The lever e, actuated by the armature of c, closes the line-connection f from the battery 9 just before breaking the earth-circuit ot' the line at h, so that there is always a path for the pulsation from the distant station.

The circuit from c bifurcates at k, and a portion of the pulsation sent passes through 6 and upon the line 7', and an equal portion of the pulsation passes through m to the artificial line composed ot'the rheostat s and ground-connection, said rheostat being adjusted to equal the resistanceof he line.

The armature-lever 0 isinoperative by the current sent, because the action of the two magnets on the same is balanced, the attractive forces of such magnets being equal; and I make the core of the magnet m to slide in the helix, and attach it to the armature-1ever 0, so that the cores-of Z and m maybe equally energized, and not influenced by the current sent, whether the armature is near the core of l or drawn baclr therefrom by the spring 3.

It will now be understood that the lever 0 will not respond when the pulsation sent passes through l m, but that the. armaturelever 0 will respond to the pulsation from the distant station, because the same only acts in l, and by this lever-'0 a'local circuit and sounder or other receiver is operated.

The pulsation sent from g upon'the line 1' is increased by the static charge, and upon cessationof the puls'ation the static charge reacts and these operations might disturb the balance between I and m. I therefore employ the mechanical compensator formed of the spring't' and notched armature-lever u, to the magnet d; hence, when the current is closed at a, and the armatures of 0 and u are attracted, tlie'motion of the lever u brings the notch atthe end of such lever across beneath the -projection on the spring it. Thereby the force of the springt is relieved, and then again bent, and when relieved the spring3 exerts its full power. And when the spring t is bent, its force lessens the power of the spring 3; hence this spring 3 is able to resist the increase of magnetism due to the static condition of the line when the circuit is closed, and to compensate for the reaction of the static charge as the circuit at a is broken, thus leaving the magnet l entirely unintluenced bythe'current sent, and capable ofthe most delicate adjustment by the spring 3 for receiving from the'distant station.

It is to be understood that the effect of the static electricity is apparent when the magnet l is charged and discharged, and that at that moment the notch inthe end of u relieves the' end of the spring t, allowing the increased power of the spring 3 to compensate for the static electricity acting in the magnet l.

I claim as my inventionl. The magnets l m, through which the current sent passes to the line, and artificial line, in combination with the armature-lever o, and sliding core, substantially as specified.

neutralizing the effect-0f the static charge in a duplex telegraph, snhstantially asset forth.

Signed by me this 19th day of August, A. D. 1874.

THOS. A. EDISON. Witnesses:

CHAS. E. SMITH, GEO. T. PINGKNEY. 

